1. Field of the Invention
This invention relates to an end press for bearing against a bottom end closure of a carton sleeve, and to a carton sleeve itself.
2. Description of the Prior Art
It is conventional for liquid packing cartons made from sheet material consisting of paperboard coated on both faces with thermoplastics to have bottom end closures in which panels are folded over onto one another and heat-and-pressure-sealed to one another, whereby at least parts of the bottom end closures consist of multiple thicknesses of the sheet material. The sealing can be performed by causing the carton sleeve to be received over a mandrel onto an end surface of which the panels are folded and by causing an end press to press the panels against the end surface of the mandrel. It is known from, for example U.S. Pat. Nos. 4,761,156; 3,971,300; 3,422,730 and 3,252,386 , and Swiss Patent 394786 for the end surface of the mandrel and/or the pressing surface of the end press to be formed with recesses and/or protrusions intended in most cases to be complementary to the thickeness variation of the bottom end closure.
Also, it is known from European Patent Application Publication 281206 for the pressing surface of the end press to be formed with a pyramidal protrusion extending over substantially the whole area of the bottom end closure, and for the mandrel end surface to be formed with a corresponding pyramidal recess, to give the bottom end closure a pyramidal form to promote stable seating of the carton.
The sealing pressure produced between the mandrel and the end press can cause the material, particularly the plastics, of the end closure to flow outwardly in the plane of the end closure and, particularly at the corners of the end closure, to produce outward protrusions. This displaced material can produce radially outward protrusions at the corners of the carton sleeve adjacent to the bottom end closure and such effect can cause cracking of the materials of the carton sleeve at those locations, particularly if the carton sleeve has a layer of aluminium foil at the inside surface of its paperboard.